The present invention relates to a device for producing containers, with an interior divided by at least one partition into separate container chambers. An extruder extrudes a tube of plasticized synthetic material from the annular gap between the outer nozzle ring and the inner nozzle core. The inner nozzle core has a guide for the synthetic material branched off out of the annular gap and at least one end-side outlet slot from which the branched-off synthetic material emerges as a partition. The partition extends continuously within the extruded tube. A welding and molding means closes the end of the tube by welding. By producing a pneumatic pressure gradient acting on the tube, the tube is expanded and is placed against the molding wall of the molding to form the container.
A device for producing a container divided by a partition into separate container chambers is disclosed in DE 1 179 356 A1. The guide for the synthetic material forming the inner partition, in the known device, has a direct connection between the downstream outlet opening of the annular gap and the outlet slot of small depth which extends diametrically in the nozzle core. Even if the friction conditions which prevail in the end area of the annular gap are kept within narrow limits to a corresponding setpoint, a uniform, desired material thickness of the partition formed can hardly be maintained in operation. When to improve the flow conditions, the outlet slot is formed with an enlarged cross section from its middle to both ends, thereby to the branching sites on the annular gap, the danger exists that the partition formed in the central area has a smaller thickness than in the edge areas.
An object of the present invention is to provide a device for producing a container with an interior divided by at least one partition into separate container chambers, characterized by an improved operating behavior.
This object is achieved in the present invention by a guide for the branched-off synthetic material placed in the area of the annular gap which is located upstream at a distance from the outlet end of the outlet slot.
In this manner, the branching site for the synthetic material is located in an area of the annular gap, upstream relative to the mouth area. Therefore, the area in which the plastic column is moving towards the downstream outlet opening has a considerable pressure gradient. By simply choosing the distance between the branching site and the outlet opening, the desired optimum flow conditions are established for the synthetic material entering the slot. By using the higher pressure level prevailing upstream of the outlet opening, the desired supply of the outlet slot for the partition to be formed can then be guaranteed for the respective viscosity properties of the extruded synthetic material.
In one advantageous embodiment, the nozzle core, as the guide for the branched-off synthetic material supplied to the outlet slot, can have at least one transverse hole as a connection between the annular gap which surrounds the nozzle core and the respective outlet slot. To adapt to the different conditions, only nozzle cores with differently arranged and dimensioned transverse holes need to be prepared to satisfy the different material properties.
In another advantageous embodiment, the nozzle core has a core tip which is screwed to it on the end side with a central screw union. The outlet slot is formed in the core tip. The surfaces of the core tip and of the following part of the nozzle core facing one another form a funnel surface and a conical surface which surrounds the central screw union. They are located at a distance from one another, and form an inlet area extending obliquely to the lengthwise axis of the nozzle and surrounding the screw union core as the guide for the synthetic material to be branched off from the annular gap and to reach the outlet slot via assigned passages in the core of the screw union. In one such embodiment, adaptation to different circumstances is made especially simple by only the core tip being replaced or its being screwed to the following part of the nozzle core. The desired change of the cross section of the inlet area arises between the funnel surface of the core tip and the opposite conical surface.